decision : tooltip refactoring

Moving the getCard method from ActivityModel to Decision.
This method get now the activity name and return the activity card.

Creating new methods :

strings_t getPredicates(string ruleName) :
Return predicates of a rule

ActivityModel* getActivityByName(string activityName) :
Return an activity, with tha activity name.

Activity card display :
- Activity name
- Start date
- End date
- Rules (if any)
- Predicates, for each rule (if any)